【Bun vs Yarn】A Package Manager Comparison and Migration Guide

Overview

There are several choices when it comes to JavaScript package managers, but recently, Bun has gained significant attention.

I originally used Yarn for frontend development, but I decided to switch to Bun—and it was surprisingly smooth! The biggest win? Faster build times! My Next.js web app's build time dropped from 4 minutes 30 seconds to just 1 minute 30 seconds. If you haven't tried Bun yet, I highly recommend giving it a shot!

In this article, we'll compare Bun and Yarn in detail, discuss when to use each, and walk through the steps to migrate from Yarn to Bun.

1. Performance (Speed & Resource Usage)

Installation Speed

Bun is known for being much faster than npm and Yarn. Here are some benchmark results:

• Mac (Medium to Large Projects)
  • bun install: ~9.6 sec
  • yarn install: ~19.5 sec
• Linux (CI Server Environments)
  • bun install: ~7.9 sec
  • yarn install: ~60.3 sec

This speed advantage is due to Bun being implemented in Zig, an alternative to C/C++, which optimizes parallel processing and caching.

Execution Speed

Bun uses WebKit’s JavaScriptCore engine, making it significantly faster than Node.js.

• Bun: 59,026 requests per second
• Node.js: 19,039 requests per second

That’s nearly 3 times faster—a huge boost in performance!

Memory Usage

However, Bun’s speed comes at the cost of higher memory consumption.

• Average memory usage in Node.js: ~40MB
• Average memory usage in Bun: ~70MB

Additionally, Bun can use more disk space after installing dependencies than Yarn, so be mindful of resource management.

Hopefully, future updates will optimize this!

2. Feature Differences

Bun’s Features

Bun isn’t just a package manager—it’s an all-in-one JavaScript runtime.

• Built-in runtime & API support (bun run for script execution)
• Fast HTTP server (Bun.serve())
• Built-in SQLite and PostgreSQL drivers
• Native support for TypeScript/JSX
• Built-in test runner (bun test)
• Hot reload functionality (auto-refresh on code changes)

Yarn’s Features

In contrast, Yarn is a dedicated package manager with the following capabilities:

• Workspaces (Monorepo support)
• Plug’n’Play (PnP) dependency management (no node_modules required)
• Extensive plugin ecosystem
• Strict version control (yarn.lock)
• Offline installation support

While Bun is feature-rich, Yarn is more mature in terms of package management and ecosystem stability.

3. Compatibility (Node.js Ecosystem)

Node.js API Compatibility

Since Yarn runs directly on Node.js, it offers full compatibility. However, Bun, being its own runtime, has a few limitations:

• Some Node.js APIs are not yet implemented
• Certain native modules (e.g., bcrypt) may not work
• Behavior may slightly differ from standard Node.js

Plug’n’Play (PnP) Support

Yarn’s PnP mode eliminates node_modules, leading to:

• Reduced disk I/O and faster startup times
• Prevention of undeclared dependencies (enhanced security)

However, some tools don’t yet support PnP, so compatibility issues may arise.

4. Migration from Yarn to Bun

1. Install Bun

For macOS users with Homebrew, install Bun using:

brew install oven-sh/bun/bun

For other installation methods, visit the official site:

• Bun - Official Website

2. Install Dependencies with Bun

Navigate to your project directory and run:

rm -rf yarn.lock
bun install

That’s it—Bun is now managing your dependencies!

3. Replace Commands

Here’s how to update your Next.js commands:

yarn dev  →  bun dev
yarn build  →  bun run build
yarn start  →  bun run start

If you’re using a Docker container, update your base image accordingly. First, check your Bun version:

bun -v

Then replace your Node.js image with:

node:<node-version>  →  oven/bun:<bun-version>

5. Summary: Which One Should You Choose?

Bun is incredibly powerful, but Yarn remains the safer choice for stability and compatibility. That said, as Bun evolves, it may become an even stronger contender.

Give it a try and see how it works for your project!